Urinary magnesium excretion and risk of hypertension: the prevention of renal and vascular end-stage disease study.

Observational studies on dietary or circulating magnesium and risk of hypertension have reported weak-to-modest inverse associations, but have lacked measures of actual dietary uptake. Urinary magnesium excretion, an indicator of intestinal magnesium absorption, may provide a better insight in this association. We examined 5511 participants aged 28 to 75 years free of hypertension in the Prevention of Renal and Vascular End-Stage Disease (PREVEND) study, a prospective population-based cohort study. Circulating magnesium was measured in plasma and urinary magnesium in two 24-hour urine collections, both at baseline. Incident hypertension was defined as blood pressure ≥140 mm Hg systolic or ≥90 mm Hg diastolic, or initiation of antihypertensive medication. During a median follow-up of 7.6 years (interquartile range, 5.0-9.3 years), 1172 participants developed hypertension. The median urinary magnesium excretion was 3.8 mmol/24 hour (interquartile range, 2.9-4.8 mmol/24 hour). Urinary magnesium excretion was associated with risk of hypertension in an inverse log-linear fashion, and this association remained after adjustment for age, sex, body mass index, smoking status, alcohol intake, parental history of hypertension, and urinary excretion of sodium, potassium, and calcium. Each 1-unit increment in ln-transformed urinary magnesium excretion was associated with a 21% lower risk of hypertension after multivariable adjustment (adjusted hazard ratio, 0.79; 95% confidence interval, 0.71-0.88). No associations were observed between circulating magnesium and risk of hypertension. In conclusion, in this cohort of men and women, urinary magnesium excretion was inversely associated with risk of hypertension across the entire range of habitual dietary intake.